What potential issue could arise in slowly permeable soils under mound systems?

In slowly permeable soils, one significant concern for mound systems is the potential for groundwater levels to rise to the surface beneath the mound. This situation can occur because slowly permeable soils do not allow water to penetrate and disperse efficiently, leading to water accumulating in the soil profile. When the rate at which water is introduced into the mound exceeds the soil's capacity to absorb it, the excess water can create a buildup of groundwater.

This elevated groundwater level poses several problems. Firstly, it can lead to the mound system failing to function properly, as proper treatment of wastewater relies on adequate soil absorption. Insufficient drainage can result in the saturation of the mound, thus compromising its ability to filter contaminants effectively. Additionally, a rise in groundwater can contribute to surface water contamination if the water from the mound surfaces, carrying untreated effluent into surrounding areas.

This problem underscores the importance of assessing soil permeability and hydrology when designing and installing septic systems, particularly in areas where soils are identified as having slow permeability. Proper design considerations must ensure that the mound system can effectively manage wastewater without risking groundwater contamination.